The U.S. will still have a troop presence in Iraq after this month, with 50,000 troops staying behind to train security forces and run counter-terrorism operations. Obama has pledged to have all troops out of the country by the end of 2011.

But as the war in Iraq dies down, Obama said the war in Afghanistan will continue full force.

"Let us never forget, it was Afghanistan where al Qaeda plotted and trained to murder 3,000 innocent people on 9/11," he said.

"And if Afghanistan were to be engulfed by an even wide insurgency, al Qaeda and its terrorist affiliates would have even more space to plan their next attack," Obama said. "And as President of the United States, I refuse to let that happen."

Despite the increase in Afghanistan, there are fewer U.S. troops serving in Iraq and Afghanistan now than when Obama took office.

When the Iraq withdrawal is complete in September, the White House said there will 146,000 troops on the ground -- down from 177,000 in January 2009.